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jdelacroix / qcx_cat_fsk

Use the QCX with FSK-type digital modes in WSJT-X using its CAT interface.
GNU General Public License v3.0
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Support Olivia MFSK #4

Open jdelacroix opened 3 years ago

jdelacroix commented 3 years ago

Jean-Pierre,

I would like to investigate modifying the QCX CAT FSK code to support Olivia digital mode at 31.25 baud. Could the Si5351 be programmed to shift frequencies at that rate? The QCX firmware version >= 1.05 supports supports a 38400 baud rate serial interface. A Set Frequency CAT command would take 3.65 mSec. A comment on the Silicon Labs forum suggested that the Si5351 settling time for a multisynth divider frequency change is only 5 clock cycles. I would like your feedback on the feasibility of implementing Olivia mode.

Thanks,

Jim N7IHQ

_Originally posted by @n7ihq in https://github.com/jdelacroix/qcx_cat_fsk/issues/1#issuecomment-761910129_

jdelacroix commented 3 years ago

My initial guess is that it should be possible to use this code to support Olivia, since it's a MFSK mode, just like FT8. Here are a few development items to work out to be sure:

  1. [ ] Measure minimum timing between tone (frequency) shifts to make sure it's feasible (e.g., serial baud rate, CAT command rate, etc.)
  2. [ ] Verify that the software is soft keying (vs. hard keying), i.e. does the output match the audio input?
  3. [ ] Implement a buffer between audio decoder and transmitting logic (i.e., a worker queue) to manage latency properly.
  4. [ ] Test Olivia with fldigi's audio output.
n7ihq commented 3 years ago

Thank you for considering supporting Olivia mode. I am a C++ beginner and do not have the knowledge or experience to modify the code.

Jim N7IHQ